I found the following experiment to produce VEPs . i cant make out if the stimuli is Patterned or unpatterened. I need to know this since otherwise i cannot figure out whether the response that will be generated later be SSVEP or Flash VEP.
Quote:
In this experiment, there were two types of events "square" and "rt", "square" events corresponding to the appearance of a green colored square in the display and rt to the reaction time of the subject.

The square could be presented at five locations on the screen distributed along the horizontal axis.

Here we only considered presentation on the left, (at about 3 degree and 1.5 degree of visual angle respectively).

In this experiment, the subject covertly attended to the selected location on the computer screen responded with a quick thumb button press only when a square was presented at this location.

They were to ignore circles presented either at the attended location or at an unattended location.